| As an environmentally friendly process, catalytic combustion of methane has been studied extensively due to the following advantages, decreasing temperature of methane combustion, increasing energy efficiency and deceasing the formation of NOx. Pd catalysts are regarded as one of the best catalysts for it, but the activity at low temperature and stability is still very poor. The Pd catalyst prepared by plasma reduction and calcination (PR&C) method can overcome these disadvantages, so the purpose of this paper is to explore the effect of preparation conditions on as-prepared Pd/HZSM-5 with XRD, chemisorption and evaluation of activity.The reaction evaluation of methane combustion indicates that as-prepared Pd/HZSM-5 shows good catalytic activity and stability at lower Pd loading. Especially for 0.5% Pd/HZSM-5, the methane conversion is two times with the conventional catalysts. Furthermore no deactivation is found for PR&C Pd catalyst during 48 h reaction. Therefore this kind of Pd catalyst can decrease the Pd loading at the same methane conversion.The XRD characterization indicates that Pd cations can be reduced to metallic phase during the plasma treatment. So plasma reduction can take the place of chemical reduction or hydrogen reduction. This environmentally friendly technique can reduce the cost. Owing to the reduction of Pd cations, the surface color of Pd catalysts is changed from brown to black. However the following calcination at high temperature results in the color recovery, this is due to the complete oxidation of metallic Pd to PdO.The chemisorption indicates that the plasma treatment can promote the Pd dispersion, especially at lower Pd loading. The Pd dispersion is increased 50% than conventional catalysts at 0.5% loading. As the increasing of calcination temperature, the Pd dispersion of as-prepared Pd/HZSM-5 increases too, especially at 973K. In conclusion, the optimum parameters for as-prepared Pd/HZSM-5 are: 0.5% Pd loading and calcination at 973K.
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